Qt: Safer GPU renderer switching

src/duckstation-qt/mainwindow.cpp

@@ -6,6 +6,7 @@
 #include "qtsettingsinterface.h"
 #include "settingsdialog.h"
 #include <QtWidgets/QFileDialog>
+#include <QtWidgets/QMessageBox>
 #include <cmath>
 
 static constexpr char DISC_IMAGE_FILTER[] =
@@ -76,26 +77,13 @@ void MainWindow::toggleFullscreen()
   m_ui.actionFullscreen->setChecked(fullscreen);
 }
 
-void MainWindow::switchRenderer()
+void MainWindow::recreateDisplayWidget(bool create_device_context)
 {
   const bool was_fullscreen = m_display_widget->isFullScreen();
   if (was_fullscreen)
     toggleFullscreen();
 
-  QByteArray state;
-  if (m_emulation_running)
-  {
-    // we need to basically restart the emulator core
-    state = m_host_interface->saveStateToMemory();
-    if (state.isEmpty())
-    {
-      m_host_interface->ReportError("Failed to save emulator state to memory");
-      return;
-    }
-
-    // stop the emulation
-    m_host_interface->blockingPowerOffSystem();
-  }
+  switchToGameListView();
 
   // recreate the display widget using the potentially-new renderer
   m_ui.mainContainer->removeWidget(m_display_widget);
@@ -104,25 +92,21 @@ void MainWindow::switchRenderer()
   m_display_widget = m_host_interface->createDisplayWidget(m_ui.mainContainer);
   m_ui.mainContainer->insertWidget(1, m_display_widget);
 
+  if (create_device_context)
+    switchToEmulationView();
+
   // we need the surface visible..
   QCoreApplication::processEvents(QEventLoop::ExcludeUserInputEvents);
 
-  if (!state.isEmpty())
+  if (create_device_context && !m_host_interface->createDisplayDeviceContext())
   {
-    // restart the system with the new state
-    m_host_interface->bootSystem(QString(), QString());
-    m_host_interface->loadStateFromMemory(std::move(state));
+    QMessageBox::critical(this, tr("DuckStation Error"),
+                          tr("Failed to create new device context on renderer switch. Cannot continue."));
+    QCoreApplication::exit();
+    return;
   }
 
-  // update the menu with the selected renderer
-  QObjectList renderer_menu_items = m_ui.menuRenderer->children();
-  QString current_renderer_name(Settings::GetRendererDisplayName(m_host_interface->GetCoreSettings().gpu_renderer));
-  for (QObject* obj : renderer_menu_items)
-  {
-    QAction* action = qobject_cast<QAction*>(obj);
-    if (action)
-      action->setChecked(action->text() == current_renderer_name);
-  }
+  updateDebugMenuGPURenderer();
 }
 
 void MainWindow::onPerformanceCountersUpdated(float speed, float fps, float vps, float average_frame_time,
@@ -214,14 +198,12 @@ void MainWindow::setupAdditionalUi()
     const GPURenderer renderer = static_cast<GPURenderer>(i);
     QAction* action = m_ui.menuRenderer->addAction(tr(Settings::GetRendererDisplayName(renderer)));
     action->setCheckable(true);
-    action->setChecked(m_host_interface->GetCoreSettings().gpu_renderer == renderer);
     connect(action, &QAction::triggered, [this, action, renderer]() {
       m_host_interface->putSettingValue(QStringLiteral("GPU/Renderer"), QString(Settings::GetRendererName(renderer)));
       m_host_interface->applySettings();
-      action->setChecked(true);
-      switchRenderer();
     });
   }
+  updateDebugMenuGPURenderer();
 }
 
 void MainWindow::updateEmulationActions(bool starting, bool running)
@@ -307,6 +289,8 @@ void MainWindow::connectSignals()
   connect(m_host_interface, &QtHostInterface::toggleFullscreenRequested, this, &MainWindow::toggleFullscreen);
   connect(m_host_interface, &QtHostInterface::performanceCountersUpdated, this,
           &MainWindow::onPerformanceCountersUpdated);
+  connect(m_host_interface, &QtHostInterface::recreateDisplayWidgetRequested, this, &MainWindow::recreateDisplayWidget,
+          Qt::BlockingQueuedConnection);
 
   connect(m_game_list_widget, &GameListWidget::bootEntryRequested, [this](const GameList::GameListEntry* entry) {
     // if we're not running, boot the system, otherwise swap discs
@@ -347,3 +331,21 @@ void MainWindow::doSettings(SettingsDialog::Category category)
   if (category != SettingsDialog::Category::Count)
     m_settings_dialog->setCategory(category);
 }
+
+void MainWindow::updateDebugMenuGPURenderer()
+{
+  // update the menu with the new selected renderer
+  std::optional<GPURenderer> current_renderer = Settings::ParseRendererName(
+    m_host_interface->getSettingValue(QStringLiteral("GPU/Renderer")).toString().toStdString().c_str());
+  if (current_renderer.has_value())
+  {
+    const QString current_renderer_display_name(
+      QString::fromUtf8(Settings::GetRendererDisplayName(current_renderer.value())));
+    for (QObject* obj : m_ui.menuRenderer->children())
+    {
+      QAction* action = qobject_cast<QAction*>(obj);
+      if (action)
+        action->setChecked(action->text() == current_renderer_display_name);
+    }
+  }
+}

src/duckstation-qt/mainwindow.h

@@ -27,7 +27,7 @@ private Q_SLOTS:
   void onEmulationStopped();
   void onEmulationPaused(bool paused);
   void toggleFullscreen();
-  void switchRenderer();
+  void recreateDisplayWidget(bool create_device_context);
   void onPerformanceCountersUpdated(float speed, float fps, float vps, float average_frame_time,
                                     float worst_frame_time);
 
@@ -48,6 +48,7 @@ private:
   void switchToGameListView();
   void switchToEmulationView();
   void doSettings(SettingsDialog::Category category = SettingsDialog::Category::Count);
+  void updateDebugMenuGPURenderer();
 
   Ui::MainWindow m_ui;
 

src/duckstation-qt/qthostinterface.cpp

@@ -105,6 +105,7 @@ void QtHostInterface::applySettings()
   }
 
   // TODO: Should we move this to the base class?
+  const GPURenderer old_gpu_renderer = m_settings.gpu_renderer;
   const bool old_vsync_enabled = m_settings.video_sync_enabled;
   const bool old_audio_sync_enabled = m_settings.audio_sync_enabled;
   const bool old_speed_limiter_enabled = m_settings.speed_limiter_enabled;
@@ -120,6 +121,10 @@ void QtHostInterface::applySettings()
   {
     UpdateSpeedLimiterState();
   }
+
+  // TODO: Fast path for hardware->software switches
+  if (m_settings.gpu_renderer != old_gpu_renderer)
+    switchGPURenderer();
 }
 
 void QtHostInterface::checkSettings()
@@ -180,6 +185,11 @@ QWidget* QtHostInterface::createDisplayWidget(QWidget* parent)
   return QWidget::createWindowContainer(m_display_window, parent);
 }
 
+bool QtHostInterface::createDisplayDeviceContext()
+{
+  return m_display_window->createDeviceContext(m_worker_thread, m_settings.gpu_use_debug_device);
+}
+
 void QtHostInterface::displayWidgetDestroyed()
 {
   m_display.release();
@@ -191,7 +201,7 @@ void QtHostInterface::bootSystem(QString initial_filename, QString initial_save_
   Assert(!isOnWorkerThread());
   emit emulationStarting();
 
-  if (!m_display_window->createDeviceContext(m_worker_thread, m_settings.gpu_use_debug_device))
+  if (!createDisplayDeviceContext())
   {
     emit emulationStopped();
     return;
@@ -383,17 +393,6 @@ void QtHostInterface::powerOffSystem()
   emit emulationStopped();
 }
 
-void QtHostInterface::blockingPowerOffSystem()
-{
-  if (!isOnWorkerThread())
-  {
-    QMetaObject::invokeMethod(this, "powerOffSystem", Qt::BlockingQueuedConnection);
-    return;
-  }
-
-  powerOffSystem();
-}
-
 void QtHostInterface::resetSystem()
 {
   if (!isOnWorkerThread())
@@ -428,44 +427,6 @@ void QtHostInterface::pauseSystem(bool paused)
 
 void QtHostInterface::changeDisc(QString new_disc_filename) {}
 
-void QtHostInterface::loadStateFromMemory(QByteArray arr)
-{
-  if (!isOnWorkerThread())
-  {
-    QMetaObject::invokeMethod(this, "loadStateFromMemory", Qt::QueuedConnection, Q_ARG(QByteArray, arr));
-    return;
-  }
-
-  std::unique_ptr<ByteStream> stream = ByteStream_CreateGrowableMemoryStream();
-  if (!m_system || !QtUtils::WriteQByteArrayToStream(arr, stream.get()) || !stream->SeekAbsolute(0) ||
-      !m_system->LoadState(stream.get()))
-  {
-    Log_ErrorPrintf("Failed to load memory state");
-    return;
-  }
-}
-
-QByteArray QtHostInterface::saveStateToMemory()
-{
-  if (!isOnWorkerThread())
-  {
-    QByteArray return_value;
-    QMetaObject::invokeMethod(this, "saveStateToMemory", Qt::BlockingQueuedConnection,
-                              Q_RETURN_ARG(QByteArray, return_value));
-    return return_value;
-  }
-
-  QByteArray ret;
-  if (!m_system)
-    return {};
-
-  std::unique_ptr<ByteStream> stream = ByteStream_CreateGrowableMemoryStream();
-  if (m_system->SaveState(stream.get()))
-    return QtUtils::ReadStreamToQByteArray(stream.get(), true);
-  else
-    return {};
-}
-
 void QtHostInterface::doBootSystem(QString initial_filename, QString initial_save_state_filename)
 {
   if (!m_display_window->initializeDeviceContext(m_settings.gpu_use_debug_device))
@@ -517,6 +478,50 @@ void QtHostInterface::createAudioStream()
   }
 }
 
+void QtHostInterface::switchGPURenderer()
+{
+  // Due to the GPU class owning textures, we have to shut the system down.
+  std::unique_ptr<ByteStream> stream;
+  if (m_system)
+  {
+    stream = ByteStream_CreateGrowableMemoryStream(nullptr, 8 * 1024);
+    if (!m_system->SaveState(stream.get()) || !stream->SeekAbsolute(0))
+      ReportError("Failed to save state before GPU renderer switch");
+
+    DestroySystem();
+    m_audio_stream->PauseOutput(true);
+    m_display_window->destroyDeviceContext();
+  }
+
+  const bool restore_state = static_cast<bool>(stream);
+  emit recreateDisplayWidgetRequested(restore_state);
+  Assert(m_display_window != nullptr);
+
+  if (restore_state)
+  {
+    if (!m_display_window->initializeDeviceContext(m_settings.gpu_use_debug_device))
+    {
+      emit emulationStopped();
+      return;
+    }
+
+    CreateSystem();
+    if (!BootSystem(nullptr, nullptr) || !m_system->LoadState(stream.get()))
+    {
+      ReportError("Failed to load state after GPU renderer switch, resetting");
+      m_system->Reset();
+    }
+
+    if (!m_paused)
+    {
+      m_audio_stream->PauseOutput(false);
+      UpdateSpeedLimiterState();
+    }
+  }
+
+  ResetPerformanceCounters();
+}
+
 void QtHostInterface::createThread()
 {
   m_original_thread = QThread::currentThread();

src/duckstation-qt/qthostinterface.h

@@ -49,10 +49,10 @@ public:
   bool isOnWorkerThread() const { return QThread::currentThread() == m_worker_thread; }
 
   QWidget* createDisplayWidget(QWidget* parent);
+  bool createDisplayDeviceContext();
   void displayWidgetDestroyed();
 
   void bootSystem(QString initial_filename, QString initial_save_state_filename);
-  void blockingPowerOffSystem();
 
   void updateInputMap();
   void handleKeyEvent(int key, bool pressed);
@@ -72,7 +72,7 @@ Q_SIGNALS:
   void emulationPaused(bool paused);
   void gameListRefreshed();
   void toggleFullscreenRequested();
-  void switchRendererRequested();
+  void recreateDisplayWidgetRequested(bool create_device_context);
   void performanceCountersUpdated(float speed, float fps, float vps, float avg_frame_time, float worst_frame_time);
 
 public Q_SLOTS:
@@ -81,8 +81,6 @@ public Q_SLOTS:
   void resetSystem();
   void pauseSystem(bool paused);
   void changeDisc(QString new_disc_filename);
-  void loadStateFromMemory(QByteArray arr);
-  QByteArray saveStateToMemory();
 
 private Q_SLOTS:
   void doStopThread();
@@ -123,6 +121,7 @@ private:
   void updateHotkeyInputMap();
   void addButtonToInputMap(const QString& binding, InputButtonHandler handler);
   void createAudioStream();
+  void switchGPURenderer();
   void createThread();
   void stopThread();
   void threadEntryPoint();